1. Field of the Invention
The present invention relates to a multi-contact input device in which various kinds of signals are input by operating a central switch by a pressing operation with an operating member, and operating a plurality of peripheral switches provided around the central switch by an inclining operation with the operating member.
2. Description of the Related Art
As shown in Japanese Unexamined Patent Publication No. 8-115641 and Japanese Unexamined Patent Publication No. 10-154445, an input device used as an input device in a VTR, a navigation system and the like is constituted such that a central switch is provided on a bottom plate of a case, a plurality of peripheral switches are provided so as to surround it, the central switch is operated by a pressing operation of the operating member and the peripheral switch positioned in a direction corresponding to an operation direction is operated by an inclining operation of the operating member.
A description will be made of the multi-contact input device disclosed in Japanese Unexamined Patent Publication No. 8-115641 and Japanese Unexamined Patent Publication No. 10-154445 in detail. The input device comprises the following three components basically. The first component is the case in which the central switch is provided on the bottom plate and the plurality of peripheral switches are provided around it. Second component is a drive unit which is provided so that it can be inclined to the periphery in the case to operate the plurality of peripheral switches. Third component is the operating member which penetrates the drive unit in an axis direction so that it can be moved, and which is elastically retained in a neutral position and inclines the drive unit by an inclining operation against its retention force.
Here, the drive unit is housed in a cup-shaped retainer member which is forced upward (opposite direction to the pressing direction) by a center return spring and the drive unit is elastically held in the neutral position by force of the center return spring. A key top in which the peripheral switches are operated is formed on a lower surface of the drive unit.
According to the conventional multi-contact input device, the peripheral switch is operated by forcibly inclining the operating member elastically retained in the neutral position against the retaining force to incline the drive unit and press a diaphragm-shaped movable point of the peripheral switch. Meanwhile, the central switch is operated by directly pressing a diaphragm-shaped movable point (snap plate) of the central switch itself by pressing operation of the operating member. That is, the central switch serves also as a retention spring which forces the operating member upward (the direction opposite to the pressing direction) to elastically retain it in an initial position.
In this constitution, according to the conventional multi-contact input device, when the operating member receives a strong pressing force in the axial direction from the outside because of a droppage and the like, excessive force is applied to the snap plate of the central switch, so that the snap plate is deformed and an operation defect is likely to be generated, which is an essential problem. Similarly, when the operating member receives a strong force in the inclining direction, excessive force is applied to the peripheral switches, so that there is a problem in which an operation defect is likely to be generated.
In addition, if an operation angle is large when the operating member is operated in an inclined position, a sense of operation is better in this kind of input device. However, because the input device is miniaturized, an increase in the operation angle of the operating member is limited, so that a sense of operation becomes poor, which is a problem also.
In view of the problem regarding a sense of operation, according to the multi-contact input device disclosed in the patent document 2, an annular elastic body is intervened between the drive unit and the cup-shaped retainer member holding this, and the drive unit is relatively inclined with respect to the retainer member, so that an over stroke is provided and thus the operation angle is increased. However, in this method, it is necessary to provide the elastic body between the drive unit and the retainer member additionally, so that a secondary problem in which the number of parts is increased is generated.